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Northern peatlands in boreal and subarctic regions store about 500 Gt of carbon (C). Understanding the fate of this large C pool under a warmer climate is important, as temperatures in northern latitudes have increased quicker than the global averages over the past 100 years. Both regional climate (e.g., temperature and precipitation) and local factors (e.g., topography) influence peatland response to climate changes. To better understand peatland response to climate changes, paleoecological techniques were used to study the C accumulation and paleohydrololgy of peatlands in different Alaskan climate regions. In addition, local-scale factors were studied through comparison of two nearby peatlands in different surficial...
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Many northern lake-rich regions are undergoing pronounced hydrological change, yet inadequate knowledge of the drivers of these landscape-scale responses hampers our ability to predict future conditions. We address this challenge in the thermokarst landscape of Old Crow Flats (OCF) using a combination of remote sensing imagery and monitoring of stable isotope compositions of lake waters over three thaw seasons (2007?2009). Quantitative analysis confirmed that the hydrological behavior of lakes is strongly influenced by catchment vegetation and physiography. Catchments of snowmelt-dominated lakes, typically located in southern peripheral areas of OCF, encompass high proportions of woodland/forest and tall shrub vegetation...
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This study demonstrates linkages between the 1997/1998 El Niño/Southern Oscillation index and a threshold shift to increased permafrost loss within a southern Taiga Plains watershed, Northwest Territories, Canada. Three-dimensional contraction of permafrost plateaus and changes in vegetation structural characteristics are determined from multitemporal airborne Light Detection And Ranging (Li DAR) surveys in 2008, 2011 and 2015. Morphological changes in permafrost cover are compared with optical image analogues from 1970, 1977, 2000 and 2008 and time-series hydro-climate data. Results demonstrate that significant changes in air temperature, precipitation, runoff and a shortening of the snow-covered season by 35 days...
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In Canada's western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. This thesis addresses questions on how and where groundwater recharge occurs. Watersheds were selected in Yukon (Fishing Branch River at Bear Cave Mountain) and the Northwest Territories at latitudes spanning from continuous to discontinuous permafrost (five tributary rivers to the Mackenzie River from Wrigley to Aklavik). All are characterized by perennial flow with open water in the winter, and discharge from sedimentary formations of karstic carbonates and evaporate...
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Numerous forest fires occurred during the summer of 2004 in the Klondike Goldfields region of the Yukon Territory, an area of extensive discontinuous permafrost. More than 35 shallow detachment failure landslides developed in subsequent weeks in Steele Creek, a small drainage basin located about 60 km south of Dawson City. Preliminary observations of the failures and near-surface thermal regime were made through freeze-up of 2004 and continued in the summers of 2005 and 2006. Detachment failures were mapped and individual sites were surveyed. Air and ground temperatures were measured in burned and unburned areas. In addition, two-dimensional DC resistivity transects were used to examine subsurface conditions in...
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Animal and plant remains, some associated with prehistoric artefacts, were collected in freezing caverns (glacieres) of northern Yukon Territory. Radiocarbon dates show that the oldest remains are Middle Wisconsinan (ca. 38 000 BP). The absence of material of Late Wisconsinan age likely indicates that the caves were infilled by ice during this cold period. Climate warming and ice melting during the Holocene allowed animals and prehistoric hunters to regularly visit these caves. Ice plugs were evidently smaller during the early Holocene than they are now.
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High-latitude regions store large quantities of organic carbon (C) in permafrost soils and peatlands, accounting for nearly half of the global belowground C pool. Projected climate warming over the next century will likely drive widespread thawing of near-surface permafrost and mobilization of soil C from deep soil horizons. However, the processes controlling soil C accumulation and loss following permafrost thaw are not well understood. To improve our understanding of these processes, I examined the effects of permafrost thaw on soil C dynamics in forested upland and peatland ecosystems of Alaska's boreal region. In upland forests, soil C accumulation and loss was governed by the complex interaction of wildfire...
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Northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). However, these ecosystems face increases in the severity, areal extent, and frequency of climate-mediated (e.g., wildfire, drought) and land-use change (e.g., drainage, flooding, and mining) disturbances that are placing the future security of these critical ecosystem services in doubt. Here we provide the first detailed synthesis of autogenic hydrological feedbacks that operate within northern peatlands to regulate their response to changes in seasonal water deficit and varying disturbances. We review, synthesize, and critique the current process-based understanding and qualitatively assess...
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Air and surface temperatures were measured for one year at five sites with different permafrost conditions near Mayo, Yukon Territory, to examine the behaviour of freezing and thawing n-factors and the relations between air and surface temperatures. During the freezing season, surface temperatures were lower where the snow cover was thin. Where snow covers were similar, surface temperatures were lower where permafrost was present. The freezing n-factor is controlled primarily by snow, but also by subsurface thermal conditions. During the thawing season, surface temperatures were higher where the near-surface thermal diffusivity allowed for rapid descent of the frost table. The thawing n-factor is primarily controlled...
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The influence of permafrost growth and thaw on the evolution of ice-rich lowland terrain in the Koyukuk-Innoko region of interior Alaska is fundamental but poorly understood. To elucidate this influence, the cryostratigraphy and properties of perennially frozen sediments from three areas in this region are described and interpreted in terms of permafrost history. The upper part of the late Quaternary sediments at the Koyukuk and Innoko Flats comprise frozen organic soils up to 4.5 m thick underlain by ice-rich silt characterised by layered and reticulate cryostructures. The volume of visible segregated ice in silt locally reaches 50 per cent, with ice lenses up to 10 cm thick. A conceptual model of terrain evolution...
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We used the CRU (1950-1959 and 2000-2009) and projected 5-GCM composite (2001-2010, 2051-2060, and 2091-2100) decadal climate forcing, ecotype (Jorgenson et al. 2008), soil landscape (Jorgenson et al. 2008), and snow (unpublished) maps of WRST to model the presence or absence of near-surface permafrost, temperature at the bottom of seasonal freeze-thaw layer and thickness of seasonal freeze-thaw layer within WRST. We produced permafrost temperature and active-layer and seasonally-frozen-layer thickness distribution maps through this modeling effort at a pixel spacing of 28.5 m. This is an immense improvement over the spatial resolution of existing permafrost maps on any part of Alaska, whether produced through the...
map background search result map search result map The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region N-factors and the relations between air and surface temperature in discontinuous permafrost near Mayo, Yukon Territory Dissolved Organic Carbon in Alaskan Boreal Forest: Sources, Chemical Characteristics, and Biodegradability Rapid runoff via shallow throughflow and deeper preferential flow in a boreal catchment underlain by frozen silt (Alaska, USA) Stream dissolved organic matter bioavailability and composition in watersheds underlain with discontinuous permafrost Cryostratigraphy and Permafrost Evolution in the Lacustrine Lowlands of West-Central Alaska Permafrost temperature records: indicators of climate change Morphology and Development of Ice Patches in Northwest Territories, Canada Encounters with Relict Permafrost in the Anchorage, Alaska, Area High-Resolution Permafrost Modeling in Wrangell-St.Elias National Park and Preserve Geochemistry and noble gases of permafrost groundwater and ground ice in Yukon and the Northwest Territories, Canada Differential Response of Alaska Peatlands to Climate Changes of the Last Millennium The impact of forest fire on permafrost slopes Klondike area, Yukon Territory Hydrological feedbacks in northern peatlands Controls on water balance of shallow thermokarst lakes and their relations with catchment characteristics: a multi-year, landscape-scale assessment based on water isotope tracers and remote sensing in Old Crow Flats, Yukon (Canada) Nitrogen retention in the riparian zone of catchments underlain by discontinuous permafrost Faunal and Archaeological Remains as Evidence of Climate Change in Freezing Caverns, Yukon Territory, Canada Thermal state of permafrost in North America: a contribution to the international polar year  Threshold loss of discontinuous permafrost and landscape evolution Differential Response of Alaska Peatlands to Climate Changes of the Last Millennium Rapid runoff via shallow throughflow and deeper preferential flow in a boreal catchment underlain by frozen silt (Alaska, USA) The impact of forest fire on permafrost slopes Klondike area, Yukon Territory Encounters with Relict Permafrost in the Anchorage, Alaska, Area Controls on water balance of shallow thermokarst lakes and their relations with catchment characteristics: a multi-year, landscape-scale assessment based on water isotope tracers and remote sensing in Old Crow Flats, Yukon (Canada) Stream dissolved organic matter bioavailability and composition in watersheds underlain with discontinuous permafrost Nitrogen retention in the riparian zone of catchments underlain by discontinuous permafrost N-factors and the relations between air and surface temperature in discontinuous permafrost near Mayo, Yukon Territory Dissolved Organic Carbon in Alaskan Boreal Forest: Sources, Chemical Characteristics, and Biodegradability Faunal and Archaeological Remains as Evidence of Climate Change in Freezing Caverns, Yukon Territory, Canada Geochemistry and noble gases of permafrost groundwater and ground ice in Yukon and the Northwest Territories, Canada The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region High-Resolution Permafrost Modeling in Wrangell-St.Elias National Park and Preserve Cryostratigraphy and Permafrost Evolution in the Lacustrine Lowlands of West-Central Alaska Morphology and Development of Ice Patches in Northwest Territories, Canada Threshold loss of discontinuous permafrost and landscape evolution Permafrost temperature records: indicators of climate change Hydrological feedbacks in northern peatlands Thermal state of permafrost in North America: a contribution to the international polar year